Fungal Diseases

Fungal diseases - an overview:

This page provides an overview of the fungal diseases in vegetable crops. The related tools listed at the end of the page provided detailed information about identification, symptoms, and management of fungal diseases. It is important to have a plant diagnostics laboratory confirm the pathogen causing any diseases in a crop so that the disease can be appropriately managed.

Fungi constitute the largest number of plant pathogens and are responsible for a range of serious plant diseases. Most vegetable diseases are caused by fungi. They damage plants by killing cells and/or causing plant stress. Sources of fungal infections are infected seed, soil, crop debris, nearby crops and weeds. Fungi are spread by wind and water splash, and through the movement of contaminated soil, animals, workers, machinery, tools, seedlings and other plant material. They enter plants through natural openings such as stomata and through wounds caused by pruning, harvesting, hail, insects, other diseases, and mechanical damage.

Some of the fungi are responsible for foliar diseases – Downy mildews; Powdery mildews; and White blister are some of the highly prevalent foliar diseases. Other fungi – Clubroot; Pythium species; Fusarium species; Rhizoctonia species; Sclerotinia and Sclerotium species – are soilborne diseases.

Small, white, powdery patches on most above-ground surfaces; usually observed first on undersides of leaves but eventually cover both surfaces; affected leaves become yellow, then brown and papery and die.

Management:

Integrated Crop Protection (ICP) or the Integrated Pest Management (IPM) approach has achieved success in the management of the fungal diseases. ICP considers the production system as a whole, including all pests and the importance of soil health. It requires a good understanding of the fungi; the periods during which the crops are susceptible; and the influence of environmental conditions.

Understand the implications for irrigation timing and minimise free moisture and high humidity periods (e.g. irrigating at around 4 am rather than at dusk, not irrigating during peak periods of spore release)